1. Field of the Invention
The present invention relates to a thermal development recording apparatus that is applied to a recording in a so-called dry system using the dry material, to which a wet process is not applied, by applying a heating process to the thermal development recording material.
2. Description of the Related Art
In the prior art, as the image recording apparatus such as the digital radiography system, CT, MR, etc. for recording the image for medical use, the wet system for obtaining the reproduced image by applying the wet process to the silver photographic photosensitive material after the photographing or recording is employed. In contrast, in recent years the recording system using the dry system in which the wet process is not executed is observed with interest. In such recording system, a film made of photosensitive and thermal recording material (photosensitive/thermal recording material) or thermal development photosensitive material (referred to as “thermal development recording material” hereinafter) is employed. Also, in the recording system using the dry system, a latent image is formed by irradiating (scanning) a laser beam onto the thermal development recording material in the exposing portion, then the thermal development is carried out in the thermal-developing portion by bringing the thermal development recording material into contact with a heating means, then such material is cooled, and then the thermal development recording material on which the image is formed is ejected to the outside of the apparatus. Such dry system can overcome the problem of the waste liquid processing in contrast to the wet process.
However, in the image recording apparatus in the prior art, such a problem existed that an inlet temperature of the cooling portion, etc. are changed by the successive processing of the thermal development recording material and as a result a density of the image is changed. In other words, a temperature in the cooling portion is increased by the successive processing of the thermal development recording material by a quantity of heat given by the thermal development recording material. Therefore, such a drawback is caused that the density of the image is thickened higher than a predetermined density. For this reason, the image recording apparatus in which the density of the image is not changed even when the thermal development recording materials are successively processed was proposed.
JP-A-2000-284382 is known as a related art.
The image recording apparatus disclosed in JP-A-2000-has a recording portion for forming the latent image by exposing the thermal development recording material, a controlling portion for executing the control of the recording portion, a thermal-developing portion for executing the thermal development by heating the thermal development recording material by virtue of the heating medium, and a cooling portion for cooling the thermal development recording material after the thermal development, and also includes a temperature sensor for measuring a temperature of the thermal development recording material before such material enter into the thermal-developing portion, a temperature sensor for measuring an inlet temperature of the cooling portion, and a quantity-of-light correcting circuit for correcting a quantity of recording light on the thermal development recording material based on outputs of these temperature sensors. According to quantity-of-light correction of the quantity-of-light correcting circuit, a quantity of light is reduced smaller as the temperature of the thermal development recording material upon entering into the thermal-developing portion becomes higher and the inlet temperature of the cooling portion becomes higher after thermal development. 
As a result, even though the number of sheets of the thermal development recording material is increased, the density can always be maintained constant.
However, in the above image recording apparatus, the density was maintained constant by reducing a quantity of light as the temperature of the thermal development recording material is increased higher and the inlet temperature of the cooling portion is increased higher. But sometimes a color tome was changed in such case. More particularly, the event that the temperature rise in the cooling portion is caused by the successive recording signifies that a thermal-developing time is substantially prolonged. Then, it became apparent that, because the thermal-developing time is extended, the color tone as the characteristic of the photosensitive material is changed. For example, as shown in FIG. 3A, the thermal development recording material on which the latent image is formed by the recording portion at the preceding stage enters into the thermal-developing portion, then such material is heated and reaches a development proceeding temperature at a time t10, and then proceed of the thermal development is started. Then, a temperature is increased, then the temperature is maintained constant by the temperature adjustment to exceed the development proceeding temperature, and then the thermal development recording material is transferred from the thermal-developing portion to the cooling portion. The proceed of the thermal development is stopped at a time t11 in the middle of this processing. In this case, a development proceeding time t1 of the thermal development recording material is given by t1=t11−t10. However, when the inlet temperature of the cooling portion is increased because of the successive processing of the thermal development recording material, a development proceed stopping time of the thermal development recording material becomes t21. As a result, the development proceeding time is prolonged by a difference of t21−t11 rather than the thermal development recording material whose development proceeds up to t1, and thus the color tone was changed correspondingly. That is, since the color tone depends on the thermal-developing time, it was impossible to maintain such color tone constant even if an mount of exposure is changed.